Image data are often subject to digital arithmetic processing to display an image with a desired image quality. One known digital arithmetic processing technology is color adjustment. Image data often include data indicating the grayscale values of respective subpixels (such as red subpixels, green subpixels and blue subpixels) of respective pixels and the colors of the respective pixels in an actual display image can be adjusted by adjusting the grayscale values of the respective subpixels through a color adjustment technology.
One example of a color adjustment technology is color gamut adjustment. A display panel (such as a liquid crystal display panel) may be insufficient in the color reproducibility and this may make it impossible to represent all the colors in a desired color gamut (for example, the color gamut defined in the sRGB standard or the NTSC (National Television System Committee) standard). In such a case, a color adjustment technology helps representing the colors in a color gamut as similar as possible to the desired color gamut.
Although various technologies have been proposed for color adjustment, the inventors find room for improvement in conventional color adjustment technologies with respect to the circuit size reduction, while achieving an appropriate color adjustment. The situation may be severe, especially when color adjustment and different image processing (such as gamma correction) are performed in serial.
Discussed below is an example in which gamma correction is performed on image data obtained by color adjustment, as illustrated in FIG. 1. In order to effectively perform color adjustment, it is desired that the bit width of the output image data obtained by the color adjustment is larger than that of the input image data. This aims to avoid gradation collapse in the color adjustment. In one example, when input image data of color adjustment represent the grayscale value of each of the red, green and blue colors with eight bits, image data which represent the grayscale value of each of the red, green and blue colors with 10 bits may be generated as the output of the color adjustment.
When gamma correction is further performed on the image data obtained as the output of the color adjustment, it is further desired that the bit width of the image data obtained as the output of the gamma correction is further increased. When image data which represent the grayscale value of each of the red, green and blue colors with 10 bits are generated as the output of the color adjustment, for example, image data which represent the grayscale value of each of the red, green and blue colors with 12 bits may be generated as the output of the gamma correction. The increase in the bit widths of the input and output image data of the gamma correction, however, undesirably increases the circuit size of a circuit used for the color adjustment.